Welcome to another MedCram lecture we're going to talk about chest
x-rays today how to interpret them how to review them in a systematic way and
make sure that you get the interpretation correct the first thing
that we've got a review is how to interpret a chest x-ray so an x-ray is
simply a film that is looking at material hitting the film and causing it
to either be dark or white it's a black and white film and that correlates to
about five different areas of density okay so everything's black and white
going from black this represents basically air
so things that are air density on the chest x-ray are going to appear black
things that are dark gray
is going to look like subcutaneous tissue or fat 3 you'll kind of see light
gray and that's usually soft tissues like the heart blood vessels things of
that nature it's a soft tissue for is going to be just off-white and this is
going to be bone so ribs clavicle things of that nature and then finally you're
going to see bright white and so this is things like metal which is sometimes
seen on chest x-rays either because of pacemakers defibrillators or even
buckshot from gunshot wounds so these are your five things that you're
generally going to see now because of these different densities you're going
to notice things on the chest x-ray if there is a difference in density by
objects that are next to each other for instance if we've got object a
sitting next to object B the only way you're going to be able to see this line
that separates them is if the density of B is of one of these five different
densities and it is different than the density of a let's give an example of
this here you've got the hemidiaphragm at the sits at the bottom of the lungs
that hemidiaphragm is made out of muscle and right below it sits the liver both
of which would be soft tissue and would be light gray okay so that soft tissue
density well right above that is the lung and the lung is air density and so
because you have two objects right next to each other
with different densities on this list
you're going to actually see that line very well now if something were to
happen in that lung let's say there were an ammonia
that pneumonia in that area is going to turn this air dense lung into a water
dense lung and so therefore this demarcating line is going to disappear
and you're not going to see it on the x-ray and so if you lose that line you
can say then that there is no demarcation there between the different
densities so you would call that a right lower lobe pneumonia that's as an
example now there are many ways of going through this in a systematic way one
that was proposed by Talley and O'Connor at the Trinity School of Medicine in
Dublin Ireland that's just one of many examples but let's go through a normal
chest x-ray and kind of go through the ABCs of how this works okay but before I
do that let me just go through a couple of basics so if you've got a person
standing which is usually the best way of doing a chest x-ray there's two ways
of doing it you can either shoot the film from front to back
which is known as an AP or from back to front which is known as a PA
posterior-anterior versus anterior posterior and it's really all about
where you put the board the board that's collecting the x-rays if the board is
behind the patient like this that's called an AP that's typically
what you don't do in a portable x-ray when the patient is in the intensive
care unit when the patient's ambulatory the board is going to go in front now
the reason why it's better to have it in front is that the heart and those
objects are going to be closest to the film and that way you're going to get
less artificial increase in size you know that when you're playing hand
puppets or puppet fingers with shadows against the wall that the farther you
move away from the wall the bigger your hand shadow is going to be and it's the
same way with x-rays the closer you are to that plate the more truer and better
focused you're going to be on getting the actual true size of that object so
in generally speaking a PA film is probably the best now with a PA
film they usually do something called a lateral film as well basically a side
view and so that way on an x-ray you're only going to see two dimension on a
lateral film you'll be able to actually make out three dimensions and you'll be
able to see things behind the heart for instance we'll just pair it as though
it's in the middle of the heart on a lateral film you'll actually be able to
see it behind the heart and be able to localize better where that object is so
generally speaking in a hospital when a patient is sick laying in a bed you're
just going to get one view an AP view which is susceptible to magnification of
the heart and the vessels in an outpatient setting where the patient's
ambulatory you're going to get a to view PA and lateral what you're not going to
get magnification artificially and you're going to be able to get a better
view now generally speaking we'd like to have patients take a deep breath in when
they shoot the film that way we can accentuate and see very well all the
different areas of the lungs however there's a couple of situations that you
should know where you want to do a exhalation film and that is when you're
trying to look for a pneumothorax and the reason for that is that's what it's
going to make the pneumothorax or the pleural air to be greatest and most
accentuated okay the other reason why you might want to do that is if there is
a delectable more specifically because that air trapping is going to be
accentuated on exhalation because all of the air is out of the lung except for
that area where air is not able to come out so these are the two areas where I
would do a film on exhalation rather than inhalation well that being said
when you approach a chest x-ray the thing that you really want to make sure
is that you're looking at the right x-ray nothing is worse it's going
through the whole process of looking at an x-ray only to realize that a it's
either the wrong patient or B it's from the wrong date and once you've got that
then you can move on to the systemic review okay so here is an x-ray
for review notice that this little marker up here which says L on it is
referring to the side of the patient remember that the right side of the
screen is always the left side of the patient and vice-versa so the first
thing that I like to do is I like to do a first a is the trachea I like to look
for the trachea as you can see it comes down in this area right here okay and
then notice that it branches this way and if you can make it out you can see
it branches this way and down like this
now looking at the trach it is important because you can tell if it's being
shifted in one direction or the other if it's being shifted in one direction or
the other that could mean the presence of a pleural effusion or atelectasis
pulling or pushing the trachea in one direction or the other
the other thing too is if the patient is intubated I can see if the endotracheal
tube is in that trachea as well and we typically want that between three to
five centimeters away from the Carina which is right there so one example of
this for instance if we had a lot of fluid on this side either inside or
outside the lung let's say we had whiting out on one side of the lung the
question is is that a pleural effusion or is that a complete and electus as' of
the right lung and the way you be able to tell is if this was a pleural
effusion a pleural effusion pushes and so the trachea would be deviated to the
opposite side however if it was an elective atelectasis is a collapsible
lung it would pull it towards the right side of the patient or the left side of
the screen the next thing I like to look at is B or bone so I'd like to look at
and compare the bony structures paying very close attention to site size shape
shadows and borders you've got the clavicles right here
okay so you can look for any kind of fractures you'll notice here there's
like a cacophony of ribs going by the ones that are very horizontal are the
posterior aspect of the ribs and then you'll see ones in the front that are
coming down these are the anterior portion so you can see if those are
fractured or not this one right up here at the top you can see here right above
the clavicle is related to the first rib you see the second ribs here as well you
can also look at the spinous processes and see if they are lined up all the way
down and you can look along the edge and see if there's any compression fractures
so these regular intervals will be disturbed if there's any compression
fracture so you can look at those as well
the other thing you can look at is for lytic lesions in the bone I don't see
any here this is a normal x-ray but sometimes you can find lytic lesions and
these are look like basically holes in the bone they're lytic lesions so they
have air density inside of bone density sometimes you can find some extra
cervical ribs which a little bit off of this but you wouldn't be able to see
that here so that's B for bone so we've covered a and B join us for the next
video where we talk about cardiac which is C thanks for joining us
you